The invention relates to eradicable inks.
Ink eradicator systems generally include two components. One component is an aqueous ink that includes a dye--typically a triarylmethane--that can be converted to a colorless form when contacted with a substance such as a sulfite reducing agent or an amine. The second component is an aqueous eradicator fluid that includes a substance that can cause the dye to convert to a colorless form. A user writes with the ink and, if correction is necessary, applies the eradicator fluid to the ink marking to decolorize the dye.
Aqueous inks used in eradicator systems often are not waterfast. In addition, aqueous inks may have a low viscosity, and low viscosity inks can be more prone to leakage than higher viscosity inks. Finally, writing instruments containing aqueous inks often include a cap so that the ink does not dry out when the pen is not being used.
Inks that are used in ball-point pens typically include largely non-volatile organic solvents, such as benzyl alcohol, phenyl cellosolve, diethylene glycol monoethyl ether, dipropylene glycol, glycerin, and propylene glycol. Ball-point pen inks tend to have a relatively high viscosity (e.g., greater than 10,000 cps).
An example of a triarylmethane that has been used in aqueous eradicable inks is Acid Blue 93, which has the following structure: ##STR1## Acid Blue 93 is not significantly soluble in many of the non-volatile organic solvents commonly used in ball-point pen inks.